some time ago at an auction, I bought a box of zero-flute countersinks. The conical shaped jobs with a hole bored through the crossection. Some of them worked fine, but others were dull to the point of not being usable. I stuffed these in an box and did not think about them until I recently saw an add in a Penn TOOl catalog which said they could be sharpened by grinding the interior of the hole.

I am wondering if anyone has sharpened these, and if so, how they did it.

wierdscience

02-15-2005, 10:52 PM

Very carefully with a Dremel or die grinder and a fine stone.I have also used Norton slip stones,but the smaller sizes are hard to find.

DR

02-16-2005, 12:01 AM

I've sharpened a number of them by grinding the outside. Years ago I was lucky enough to pick up a Weldon radial relief grinding fixture specially designed for the "fish eye" style.

Never tried grinding the inside of the hole, but I don't see why that wouldn't work provided you don't remove too much material. As the hole gets larger the cutting edge gets weaker. Of course, the same thing happens when too much material is removed by grinding the outside.

Thrud

02-16-2005, 12:12 AM

<font face="Verdana, Arial" size="2">Originally posted by wierdscience:
Very carefully with a Dremel or die grinder and a fine stone.I have also used Norton slip stones,but the smaller sizes are hard to find.</font>

I do the same thing with uniflute CS - only I use Diamond burrs at 20K rpm - I like the razor sharp as I use them in wood and aluminum.